北江流域抗生素污染水平和来源初探

北江是发源于湖南(武水)和江西(浈水),汇于广东韶关,流经广东全境并入海的三大河流之一。为了解整个北江抗生素污染情况,共设置44个采样点,并采集了河水及部分沉积物样品,较全面地分析了各样品中12种典型抗生素含量并初步探究了其污染来源。研究发现,包括北江源头在内的全河段均有抗生素的检出,5类抗生素在表层水和沉积物中的平均浓度分别为77.8 ng·L~(-1)和3.6 ng·g~(-1)。其中,大环内酯类污染最为严重,其含量范围为11.7~114.6 ng·L~(-1)和0~435.3 ng·g~(-1),远高于其他类抗生素。表层水中磺胺类的磺胺甲恶唑和氯霉素类的检出率达100%,其中以磺胺甲恶唑(14.7 ng·L~(-1))和阿奇霉素(25.0 ng·L~(-1))为主,而沉积物中以阿奇霉素(35.9 ng·g~(-1))、氧氟沙星(5.4 ng·g~(-1))和四环素(3.3 ng·g~(-1))为主。由于流域污染源种类和数量不同,各抗生素在北江中的分布也存在差异。表层水中抗生素含量水平表现为下游高于上中游,在沉积物中则主要集中于中、下游之间河段。这反映了人类活动强度对北江抗生素污染的直接影响。

Occurrence and Potential Sources of Antibiotics in Beijiang River, Southern China

The Beijiang River is one of the three major rivers which flow cross the Pearl River Delta Region, southern China. It serves one of the most densely urbanized regions in China and was heavily impacted by agricultures and aquacultures in recent 30 years. As emerging pollutants, there are less complete database on antibiotics and their pollution sources in the river environments. To gain insight into the occurrences, distributions and possible sources of antibiotics in the whole Beijiang River, 44 water samples and 23 sediment samples were collected along the river from source to estuary. Total 12 common antibiotics including 4 sulfonamides (sulfadiazine, sulfamethazine, sulfamethoxazole and sulfacetamide), 2 quinolones (norfloxacin and ofloxacin), 4 macrolides (roxithromycin, erythromycin, azithromycin and clarithromycin), chloramphenicol and tetracycline were investigated in these samples. The selected compounds in the samples were pretreated using solid phase extraction (SPE) followed by the determinations of high performance liquid chromatography-tandem electrospray ionization mass spectrometer (HPLC-MS/MS). The results showed that most of the antibiotics could be detected in all the samples including those from headwater areas less impacted by human activities indicating that the antibiotics were ubiquitous in the environments of the Beijiang River. The average concentrations of all antibiotics were 77.8 ng·L^-1 in the surface water and 3.6 ng·g^-1 in the sediments, respectively. The macrolides were the dominant pollutants with their concentration ranging from 11.7 to 114.6 ng·L^-1 in the surface water and 0~22.8 ng·g^-1 in the sediments, followed by quinolones (0~113.1 ng·L^-1, 0~47.1 ng·g^-1) and sulfonamides (6.7~41.5 ng·L^-1, 0~1.3 ng·g^-1). Generally, there were higher levels of antibiotics detected in the water samples adjacent to downstream and in the sediment samples between mid- and downstream than those in the upstream river. The total concentrations of most of the sediment samples were below 16 ng·g^-1 excluding several sites close to obvious pollution sources such as hospital, intensive feeding swine farm and aquaculture ponds. Moreover, some antibiotics like sulfamethoxazole and chloramphenicol could be frequently detected in all the water samples, though the uses of chloramphenicol have been limited for many years due to its adverse effects. It could be considered to be related to the illegal uses in livestock breeding. Furthermore, sulfamethoxazole (14.7 ng·L^-1) and azithromycin (25.0 ng·L^-1) were predominant in the surface water, and azithromycin (35.9 ng·g^-1), ofloxacin (5.5 ng·g^-1) and tetracycline (3.3 ng·g^-1) in the sediment samples depending on their differences in source emissions and physicochemical properties like hydrophobicity and/or absorptivity on the suspend particles. Additionally, the spatial distributions of the target antibiotics could be effected by complex hydrodynamic conditions, locations and dilution effect in the river environments. However, higher levels of antibiotics appeared at most sampling sites adjacent to the big cities such as Shaoguan, Qingyuan, Foshan and Guangzhou. The emissions from waste water treatment plant (WWTP), and other complex human activities highlighted the anthropogenic impacts on the dissemination of antibiotics in the river environments.